Abstract: Nano-sized ZnO particles were prepared by using zinc sulfate and sodium hydroxide as raw materials in the membrane dispersion micro-structured reactor by rapid mixing precipitation.The mixing scale model was used to simulate the precipitation process of nucleation,growth and agglomeration in the membrane reactor.Modeling results showed that particle nucleation dominated in the initial 0.6 ms,and after 1.6 ms,growth dominated.At the same time,due to a large number of particles,particles collision would cause aggregation,resulting in specific distribution of particle size.Mixing scale and reactant concentration had a great influence on particle diameter and distribution.Simulation results showed that when mixing scale reduced from 50 μm to 5 μm,average diameter of nano-ZnO particles decreased to 12 nm from 19 nm.Experimental results showed that with the decrease of membrane pore size,average diameter of nano-ZnO particles dropped down from 20 nm to 11 nm,and when initial reactant concentration increased from 0.05 mol·L^-1 to 0.20 mol·L^-1,average diameter of ZnO nanoparticles increased from 10 nm to 16 nm.Simulated average particle diameter and its distribution agreed well with the experimental values.

Key words: membrane dispersion micro-reactor, nano-ZnO, mixing scale model, particle size distribution

摘要： 以硫酸锌和氢氧化钠为原料,在膜分散微结构反应器中通过快速均匀混合制备得到颗粒平均尺寸为10～20 nm的氧化锌,并利用混合尺度模型模拟了微反应器内纳米颗粒的成核、生长和团聚过程。模拟计算结果表明,在最初的0.6 ms内颗粒成核占主导地位,在1.6 ms以后以生长为主,同时由于颗粒数密度较大,颗粒运动碰撞造成团聚效应,使得颗粒尺寸具有一定的分布。混合尺度和反应物浓度对颗粒直径和分布有很大影响。模拟结果表明当混合尺度从50 μm减少到5 μm,纳米氧化锌颗粒从19 nm降低到12 nm。微反应器制备实验结果表明,随着膜孔径的减小,混合强度增加,纳米氧化锌颗粒平均直径从20 nm 降低至11 nm,当初始反应物浓度从0.05 mol·L^-1提高到0.20 mol·L^-1,氧化锌纳米颗粒尺寸由10 nm增大至16 nm。颗粒平均直径及分布的模拟值与实验值相符较好。

关键词: 膜分散微反应器, 纳米氧化锌, 混合尺度模型, 颗粒分布